void bigint_mul(word z[], size_t z_size, const word x[], size_t x_size, size_t x_sw, const word y[], size_t y_size, size_t y_sw, word workspace[], size_t ws_size) { clear_mem(z, z_size); if(x_sw == 1) { bigint_linmul3(z, y, y_sw, x[0]); } else if(y_sw == 1) { bigint_linmul3(z, x, x_sw, y[0]); } else if(sized_for_comba_mul<4>(x_sw, x_size, y_sw, y_size, z_size)) { bigint_comba_mul4(z, x, y); } else if(sized_for_comba_mul<6>(x_sw, x_size, y_sw, y_size, z_size)) { bigint_comba_mul6(z, x, y); } else if(sized_for_comba_mul<8>(x_sw, x_size, y_sw, y_size, z_size)) { bigint_comba_mul8(z, x, y); } else if(sized_for_comba_mul<9>(x_sw, x_size, y_sw, y_size, z_size)) { bigint_comba_mul9(z, x, y); } else if(sized_for_comba_mul<16>(x_sw, x_size, y_sw, y_size, z_size)) { bigint_comba_mul16(z, x, y); } else if(x_sw < KARATSUBA_MULTIPLY_THRESHOLD || y_sw < KARATSUBA_MULTIPLY_THRESHOLD || !workspace) { basecase_mul(z, z_size, x, x_sw, y, y_sw); } else { const size_t N = karatsuba_size(z_size, x_size, x_sw, y_size, y_sw); if(N && z_size >= 2*N && ws_size >= 2*N) karatsuba_mul(z, x, y, N, workspace); else basecase_mul(z, z_size, x, x_sw, y, y_sw); } }
/* * Multiplication Operator */ BigInt operator*(const BigInt& x, const BigInt& y) { const size_t x_sw = x.sig_words(), y_sw = y.sig_words(); BigInt z(BigInt::Positive, x.size() + y.size()); if(x_sw == 1 && y_sw) bigint_linmul3(z.mutable_data(), y.data(), y_sw, x.word_at(0)); else if(y_sw == 1 && x_sw) bigint_linmul3(z.mutable_data(), x.data(), x_sw, y.word_at(0)); else if(x_sw && y_sw) { secure_vector<word> workspace(z.size()); bigint_mul(z.mutable_data(), z.size(), x.data(), x.size(), x_sw, y.data(), y.size(), y_sw, workspace.data(), workspace.size()); } if(x_sw && y_sw && x.sign() != y.sign()) z.flip_sign(); return z; }
/* * Squaring Algorithm Dispatcher */ void bigint_sqr(word z[], size_t z_size, const word x[], size_t x_size, size_t x_sw, word workspace[], size_t ws_size) { clear_mem(z, z_size); BOTAN_ASSERT(z_size/2 >= x_sw, "Output size is sufficient"); if(x_sw == 1) { bigint_linmul3(z, x, x_sw, x[0]); } else if(sized_for_comba_sqr<4>(x_sw, x_size, z_size)) { bigint_comba_sqr4(z, x); } else if(sized_for_comba_sqr<6>(x_sw, x_size, z_size)) { bigint_comba_sqr6(z, x); } else if(sized_for_comba_sqr<8>(x_sw, x_size, z_size)) { bigint_comba_sqr8(z, x); } else if(sized_for_comba_sqr<9>(x_sw, x_size, z_size)) { bigint_comba_sqr9(z, x); } else if(sized_for_comba_sqr<16>(x_sw, x_size, z_size)) { bigint_comba_sqr16(z, x); } else if(x_size < KARATSUBA_SQUARE_THRESHOLD || !workspace) { basecase_sqr(z, z_size, x, x_sw); } else { const size_t N = karatsuba_size(z_size, x_size, x_sw); if(N && z_size >= 2*N && ws_size >= 2*N) karatsuba_sqr(z, x, N, workspace); else basecase_sqr(z, z_size, x, x_sw); } }